


each of a pair of things intended to complement or match each other

by thesunkenship



Category: Naruto
Genre: Alpha/Beta/Omega Dynamics, Alpha/Omega, Begging, Consent is Sexy, Eventual Smut, M/M, Masturbation, Mating Cycles/In Heat, Tags to be added, plot is the best foreplay to porn
Language: English
Status: In-Progress
Published: 2017-05-27
Updated: 2017-06-14
Packaged: 2018-11-05 13:17:46
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 8,607
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11014227
Author URL: https://archiveofourown.org/users/thesunkenship/pseuds/thesunkenship
Summary: Kakashi is walking towards the memorial stone, not making any effort at all to disguise the fact that he’s blatantly ignoring everyone he passes, when he realises that he hasn’t seen Gai for days. The past week has been remarkably spandex free. No shiny bowl cuts. No dynamic entrances. There hasn’t even been a single ridiculous challenge to complete.That’s… worrying, actually.a/b/o fic.





	1. Chapter 1

Kakashi is walking towards the memorial stone, not making any effort at all to disguise the fact that he’s blatantly ignoring everyone he passes, when he realises that he hasn’t seen Gai for days. The past week has been remarkably spandex free. No shiny bowl cuts. No dynamic entrances. There hasn’t even been a single ridiculous challenge to complete. 

That’s… worrying, actually.

Coming to a halt in the middle of the street, Kakashi starts to rack his brain for what might have happened. 

He would have known if Gai were either dead or dying, so those two worst-case scenarios can be quickly dismissed. Someone would have made a point of telling him. The whole eternal rivalry thing tends to make people assume that Kakashi wants status updates on Gai’s various injuries and hospital stays. God forbid that he would ever actually visit Gai in the hospital, or send a get-well-soon card, or whatever it is that people expect him to be doing with the information that they give him.

Gai definitely isn’t on a mission. Again, Kakashi would have known. He makes a habit of checking the mission rosters every morning. It’s nice to know when his close acquaintances are going to be out of the village, he tells himself, so that he can make sure their house plants are well looked after. It might also be connected to an obsessive need to keep tags on the wellbeing of the people close to him.

If Gai were on holiday, Kakashi would have known. For one thing, Gai doesn’t seem to believe in taking time off. Hard work, the springtime of youth, and all that. For another, the one and only time Gai decided that he wanted to play the tourist he had spent the entire month leading up to his trip to Whirlpool trying to convince Kakashi to go with him. Of course, he’d been wildly unsuccessful.

So, if Gai were out the village, either on official business or not, Kakashi would know about it. That leaves the possibility that Gai is in the village and yet has been inexplicably absent from Kakashi’s day-to-day life.

He can’t remember the last time Gai got sick.

Is this an elaborate challenge? A game of hide and seek that Gai forgot to tell Kakashi they were playing? Kakashi frowns to himself. It isn’t beyond the realm of possibility. But then again, Gai is usually so deliberately transparent in establishing the rules of any of their challenges. It would be unlike him to leave Kakashi in the dark. 

He pushes aside the rising feelings of dread in his stomach. There has to be a reasonable explanation for Gai’s disappearance. He probably just set himself a ridiculous penalty for failing to complete a self-imposed challenge and was caught up completing it. Two years ago, when they were both sixteen, Gai had spent an entire week camped out on Training Ground Eight, the one with the big waterfall, doing something to do with press-ups and heavy weights. Kakashi’s memory of the challenge itself (or was it a penalty?) is hazy, but the point stands that Gai’s done it before and he might well be doing it again.

After a brief internal struggle, Kakashi decides that there’s little point in trying to do anything productive with his day until he has proof that Gai is alive and well. Glancing mournfully in the direction of the memorial stone, he turns on his heel and heads towards the training grounds. 

Gai’s challenges have been as reliable as clockwork for years now. They’re part of Kakashi’s routine, and damn it if Kakashi doesn’t cling to his routines like a mollusc clinging to a rock. Gai is like the algae growing all over Kakashi’s rock. Not necessarily invited in the first place, but a natural and healthy part of the background scenery. Pleased with the analogy, Kakashi pulls out his copy of Icha Icha and hold it up in front of his face as he walks. He doesn’t read it, but it’s reassuring just to have it there.

First, he’ll scope out the training grounds, and then the Jonin standby station, and then the main street leading to the Hokage’s tower, and then Gai’s apartment. After that, he’ll have to make the difficult choice between either asking the other Jonin whether they’ve seen Gai lately or breaking into the classified records in the Hokage’s office. 

Hopefully it won’t come to that. The decision between ruining years’ worth of careful work maintaining a cool façade and outright criminal activity is not one that Kakashi is eager to make.

Thankfully, Kakashi doesn’t need to go any further than Training Ground Two before his eye catches on familiar green spandex. Coming to a stop just outside the clearing, Kakashi looks the other man up and down, surreptitiously checking for injuries. 

There’s nothing wrong with him. 

Kakashi turns to leave, as silently as he arrived, but pauses. Gai’s not injured, but there’s something different about him. It niggles in the back of Kakashi’s mind but he can’t put his finger on it. 

There are no signs that Gai’s operating at anything less than peak condition. If anything, it looks like he has more energy than usual, as impossible as that sounds. Even from a distance the strength and power of his body is apparent. His movements are fluid. His musculature is as enviable as ever. The hair is the same. The godforsaken green jumpsuit is the same. Even the face-splitting grin is the same when Gai spots him lurking in the treeline.

Oh.

Surprised, Kakashi holds up a hand to give him a little wave. That’s certainly different. As far as he knows, Gai’s never caught him out like that before. 

“Kakashi!” Gai calls out, turning bodily to face him and wiping his hands down on his thighs. “Are you here to challenge me, rival?” His whole face lights up in excitement.

“Not really,” Kakashi replies offhandedly, sauntering into the clearing. He doesn’t want to ask Gai outright what’s changed, so he’ll have to find a way of subtly prompting the other shinobi into offering up the information.

Gai doesn’t so much as twitch at the blatant rejection. Instead he moves forwards, meeting Kakashi halfway. “I apologise for my absence. It happened very suddenly. I can only imagine your disappointment at missing two of our scheduled challenges. Never fear, Rival, I’ll make it up to you!”

“Oh? Suddenly?” Kakashi says, studiously ignoring the rest of what Gai says.

Gai laughs and claps him on the back. “Of course! You must remember from our classes at the academy! Once your presentation is set off, there’s nothing you can do to stop it. I was lucky to be alone in my apartment at the time.”

Oh. That explains it. Gai presented as an alpha and his first rut. It makes sense. Eighteen is about the right age. And of course, Gai would be an alpha, just look at him. The proportions of his body, with his wide shoulders and height, are text-book examples of his endotype.

“I look forward to you presenting as an alpha, too, dear rival,” Gai continues in earnest. “Although I have beaten you to reaching the full glory of the Springtime of Youth, it will not diminish the splendour of your own rite of passage.” He flashes his signature thumbs up.

Was Gai… reassuring him? Kakashi blinks slowly in the other man’s direction.

Not waiting for a reply, Gai soldiers on. “It’s very exciting. I feel a new power in my body! A sharpness to my senses! It was my nose that told me you were in the trees.” He taps his nose conspiratorially. 

“That’s nice,” Kakashi says, pulling his book out of his back pocket in an exaggerated show of disinterest.

“Dearest rival, there will be so many more things we can compete over!” Gai gushes. “Who can win the prettiest mate! Who can sire the most children! Who can best satisfy their mate!” Stars are swimming in his eyes.

None of those things sound particularly appealing, but Kakashi decides that he can afford to humour Gai, seeing as the man is so thrilled to be an Alpha and practically giddy at the prospect of everything that involves. “You know, I don’t think comparing mates is the best idea you’ve ever had,” he teases.

Gai laughs, tossing his head back, and throws an arm over the other man’s shoulders. Usually, Kakashi won’t stand for anyone touching him, or being in his personal space, but he doesn’t mind it so much when it’s Gai. Gai makes himself an exception to the rules.

...

Routine re-establishes itself the next day when Gai jumps out to challenge him on his way back from the Memorial Stone. The spandex and bowl cut are the same, but Kakashi suspects that the dynamic entrance is slightly more dynamic than usual.

If he didn’t know better he would think that Gai was trying to make it up to him for his absence. Actually, that’s exactly what’s happening. 

Kakashi sighs in resignation and gestures for Gai to lead the way. He doesn’t bother with any other token gestures of resistance this time. Gai did wait until after he had finished at the Memorial Stone, after all, which was considerate, and good behaviour deserves a reward.

Anyway, there are definitely worse ways to spend a Tuesday afternoon than sitting out in the sun and playing chess. The birds are singing, there’s a warm breeze in his hair, and no one is actively trying to murder him. Things could be much worse.

Gai studies the board with a look of intense concentration on his face and shifts forwards to get a view of the game from another angle. The movement makes one of Gai’s knees rubs up against Kakashi’s inner thigh. Kakashi glances at Gai, but the other man seems oblivious to the contact, too intent on planning his next move. 

A tingle of heat runs through Kakashi’s body, making his cheeks flush ever so slightly. He’s achingly aware of the point of contact between their bodies and all of his thoughts have centred in on the feeling of gentle pressure. He could easily shift his own leg a few centimetres and break the connection, and that would usually be his immediate and instinctive reaction. Except it isn’t his immediate reaction this time. He doesn’t want to move out of the way. 

He might be imagining it, but it feels like warmth is radiating outwards from the point of connection, moving both up and down his leg: curling in his belly and stroking down his calves. It’s not unpleasant to be close to Gai. There’s something reassuring about being near him, even. Kakashi starts to lean forwards, to press himself further in to the contact, chasing after the feeling of warmth and comfort. 

He catches himself just in time, realising what he’s about to do, and aborts the movement forwards. 

Kakashi blinks twice, dispelling the mist that had descended on his brain. That could have been embarrassing. He’s surprised at himself. He glances at Gai, who is thankfully still investing the vast majority of his processing capacity in studying the chess board, and forces himself to relax.

Maybe he’s dehydrated. That might explain it. Or, if he’s being really honest with himself, maybe there was some truth in what Rin had once said about him being touch-starved. He had reacted badly to the conversation at the time, so she had never mentioned it to him again, but he thinks that she might have had a quiet word with Minato. The man had started to go out of his way to draw him in to one-armed hugs and ruffle his hair. Maybe it’s been so long since he’s touched another person for an extended length of time that didn’t involve violence that he really is touch-starved.

Or he’s dehydrated and it’s making him act strangely. You never know. 

Kakashi makes the executive decision to not react in any way whatsoever to Gai’s knee pressing against his thigh, and mentally creates a list of things to worry about later. He’s still feeling warm and tingly, but it’s not an unpleasant feeling. After the game is finished he’ll take a short nap in the shade and then he’ll be feeling right as rain.

“You know,” He says mildly, addressing Gai to distract himself from his own thoughts. “If you think too hard you might hurt yourself.”

Gai laughs, loud and open and joyous. His picks up his Queen and in one sweeping gesture uses it to take out a Knight. “Your move, rival.” He arches his brows in a playful challenge.

Humming thoughtfully, Kakashi uses one finger to slide his Castle across the board. “Check mate,” he says and smiles at the way Gai is gawping in horrified mystification at his own King.

Kakashi wins the challenge. 

Gai, ever gracious in defeat, buys them both ice cream. And when his shoulder rubs up against Kakashi’s as they walk towards the Jonin standby station, Kakashi resists the overwhelming urge to lean in to the touch and, once again, makes the executive decision to not react in any way.

...

“Best of three!” Gai announces, with his hands on his hips. A week has passed since Kakashi’s success in chess. “Victory is achieved when your opponent has been immobilised for three seconds. No jutsu. No biting. No weapons of any kind. And no counting the seconds inappropriately fast.” He holds up a finger for each of the fouls and then looks over at Kakashi expectantly.

Kakashi knows that Gai’s waiting for him to approve the ground rules being laid out for their imminent wrestling matches, and that this is an opportunity to clarify anything that might be unclear or to express any discomforts he might have. 

Humming thoughtfully, he lifts up his left hand and wiggles his fingers, mimicking Gai’s pose. He points to his fourth finger, the one matching the last foul that Gai announced, and says, “How would you define ‘inappropriately fast?’”

Gai chuckles. “You know exactly what I meant, rival. We both know how long three seconds lasts!”

Well, he can’t argue with that. Kakashi inclines his head in acquiescence. A moment later, he wiggles his third finger. “Wouldn’t you say that our bodies count as deadly weapons? We are shinobi, you know.” He says conversationally.

This time, Gai doesn’t dignify his teasing with an answer. Instead, he huffs out an exasperated breath and backs away to put a few meters of distance between the two of them. “Starting positions!” He announces. The fond smile on his face is replaced by a look of steely determination. His mouth sets in a firm line and his eyes sharpen. 

Right, time to get to business then.

Kakashi bends at the knees, shifting his weight back and forth. This will be the first time they’ve fought since Gai presented as an Alpha. Kakashi wonders to what extent it will have affected the other man’s stamina and whether his instinctual reactions in battle have shifted. His body is undoubtedly thrumming with testosterone. 

Gai is both bigger and stronger than him. If it comes down to brute force he will undoubtedly be overpowered. With that in mind, Kakashi’s strategy is to stay as light on his feet as possible and avoid engaging head-on. 

Gai lunges forwards and Kakashi dodges to the left, turning quickly to hook a leg behind Gai’s ankle and place a hand against his upper back. He pushes hard. It’s a move that capitalises on Gai’s momentum and uses it against him. Before he can follow through and press his advantage, Gai drops into a forward roll. With his weight having been braced against Gai’s upper back, Kakashi loses his balance and topples forwards.

Kakashi falls to the floor and lands on his front, catching himself on his elbows and forearms. Before he can blink, Gai is on top of his, using his weight to press the smaller man’s body flat to the dirt. Straddling Kakashi’s upper thighs and pinning each wrist with a big, calloused hand, Gai calmly, and ever so slowly, starts to count.

Kakashi arches up, pushing back against Gai's body in an attempt to dislodge him. Gai's counting falters, but he maintains the upper hand by flattening his upper body against the other man and by shifting forwards so that he's straddling Kakashi higher on his thighs. 

They were close before, but now there's no space at all between their bodies. Kakashi can feel every hard inch of Gai's body pressed against him. A voice whispers in his head that this is what it would be like to be mounted by Gai, with Gai looming on top of him, pelvis pressed against his rear and hot breath tickling his ear. Overpowered and dominated. A shiver runs down his spine. 

Colour rises in Kakashi's cheeks, thankfully disguised by his mask. The same feeling of heat and warmth is rising in him as it did when they were playing chess, racing through his veins and licking at his insides, but instead of it reaching outwards from one small epicentre of contact like before, it's throbbing through his entire body. It aches. 

It makes him want to take his clothes off and jump in the river. It makes him want to take his clothes off and rub himself against Gai. No, he definitely shouldn’t do that. It's hard to think clearly when everything is just so hot. He stops struggling, letting Gai pin his body down without resistance. His head is spinning. Gai isn’t holding him in a way that would obstruct his airways, so why is he so short on breath? He's vaguely aware that Gai has started to count again. He concentrates on his breathing, keeping is steady and even, fighting the need to pant and gulp air into his lungs. 

Gai rolls off of him and jumps to his feet. The fire in his body recedes, but only enough for him to focus on the moment. He blinks slowly. The effort it would take to push himself up and on to his feet is impossibly enormous.

“You’re going easy on me rival!” Gai proclaims, extending a hand to Kakashi. Kakashi takes it, head still spinning, and Gai pulls him to his feet in one smooth motion. A quiet voice in his head whispers that Gai is strong enough to provide and protect – a real Alpha, a worthy mate to any Omega.

What a strange thought.

Kakashi nods in thanks. Gai is staring at him and he’s not sure why. He’s knows that he’s breathing normally because almost all of his conscious thought is focused on regulated it into a steady inhale and exhale. Oh, it’s because he’s still holding on to Gai’s hand, clutching it like a lifeline. 

He drops Gai’s hand and steps away, almost tripping over his own feet. Something is very, very wrong with him and he has no idea what.

Gai clears his throat. His eyebrows are drawn together in concern. “Kakashi, if you are feeling unwell we can do this another day.”

“No.” Kakashi says, but it comes out as shaky as he’s feeling so he tries again. “No, I’m fine. Let’s continue.” He’s not fine. He’s so far from fine that he’s thinking about voluntarily checking himself into the hospital. He’s only saying so because his knee jerk reaction is to hide and deny any signs of vulnerability. Habits like that are hard to break, even when your whole body is rebelling against you.

“If you’re sure.” Gai sounds unconvinced, but he doesn’t push the issue. 

Kakashi gives him a sharp nod, not trusting himself to speak. The haze is clearing and a sense of clarity is starting to return. He can make it through this.

Gai hangs back, frowning, unwilling to attack him. 

Kakashi makes to initiate contact, reasoning that they sooner they start then the sooner Gai can win another round and this will all be over with. He grabs Gai by the upper arms, intending to force Gai into engaging with him. Feeling as weak as he does, Gai should be able to pin him in a matter of moments. 

That plan is short-lived. Without warning, his legs give out beneath him and he collapses to his knees in front of the other man. Gai follows him down a moment later, having grasped him by his forearms in an attempt to steady him.

“Kakashi?” The man’s voice is strained with worry.

Kakashi is dazed and confused. The fire in his body and the haze in his mind come rushing back at full force, hitting him like a tonne of bricks. His head feels heavy and the world is spinning so he lets his forehead fall to rest against Gai's shoulder. He draws in a long, stuttering breath. Gai smells good. Really good. So Kakashi presses his nose into the crook of Gai's neck and breathes in deeply. 

“Kakashi?” Gai says again, louder this time. 

It jolts him out of his daze. He jerks back, snapping his head up and away from Gai’s scent glands. He shouldn’t have done that. It was inappropriate. Far too intimate a gesture than is right between friends. 

He’s mortified to discover that he’s completely erect.

Kakashi opens his mouth, intending to apologise, but all that comes out of his throat is a quiet, broken whimper.

Gai’s mouth sets in a grim line and his grip tightens on Kakashi’s arms. The way they’re holding on to each other could easily be mistaken for a lover’s embrace. “You need to tell me what’s wrong, Kakashi.” He’s serious and earnest, but he can’t quite hide his alarm. 

The problem is that Kakashi doesn’t know what’s wrong. All he knows is that the heat in his body is building and building, and that his clothes are rubbing and scratching against his skin and he needs to take them off, and that he has never in his life wanted so badly to be close to anyone as he wants to be close to Gai right now. 

There’s an unfamiliar stirring in his groin. He feels a wetness run down the inside of his thigh. It’s not much, not enough to even soak through his trousers, but it’s enough to explain what’s happening to his body.

He’s presenting as an omega.

Gai’s nose twitches. It takes a moment for him to process what he’s smelling. His eyes widen and his mouth drops open. He stares at Kakashi, stunned beyond words.

Kakashi stares right back, making no attempt to disguise his own shock.


	2. Chapter 2

**Summary for the Chapter:**

> Short Gai POV

Gai drops Kakashi onto the single bed, a limp tangle of limbs, and all but runs for the door. He pulls the door shut behind him, using more force than is strictly necessary in his haste to get out of the room, and sinks to the floor, his back to the dark wood, trapping Kakashi inside and preventing anyone else from getting in. He looks down at his hands and observes that they’re shaking. 

The moment he realised that Kakashi was going into heat in the middle of the training ground, he had picked the other man up, hauling him into his arms, and ran across the village to get him to safety. Kakashi hadn’t even protested being man-handled, and that in itself had been deeply unsettling.

It would be unfair to fully attribute Gai’s actions to his primal instincts, the Alpha part of his brain demanding that he protect an Omega, when his immediate thought had been that Kakashi would hate for people to see him like this. Kakashi is an intensely private person. He’s worn a face mask religiously since being a young child. Gai has never even seen his actual face. No one has seen his face. This, right now, is not something he would appreciate anyone knowing about, much less witnessing. More than that, it was unsafe to stay in the training ground. 

His friend, his best friend, was vulnerable and confused and needed to be somewhere secure to ride out what Gai knew would be a messy and distressing experience.

Kakashi moans, low and breathy, the sound carrying easily through the closed door. Gai twitches, his hands curling and uncurling into fists against his thighs. His whole body is tense, muscles rigid, fighting the impulse to leap to his feet and rush to the Omega's side. 

He has to stay in the hallway. He can’t allow himself to re-enter the room. He has to control himself.

There’s a voice in the back of his head screaming at him that he’s only meters away from an Omega in heat. A pliant, willing, fertile Omega who smells like lust and health and home. All he has to do is stand up, walk into the room, and propose that he satiate the burning in the other man’s body. Kakashi wouldn’t say no, whispers the voice, not when he’s like this. He’s desperate and in pain.

Gai drops his head into his hands, pushing into his eye sockets with the palms of his hands in an attempt to ward away the intrusive thoughts, and groans. He’s not an animal and he would never stoop that low. Kakashi trusts him and he would rather die than betray that trust. Kakashi’s not in his right mind. He can’t consent like this. It would be wrong.

Gods, Kakashi smelt so good though. Remembering the way that he had clutched at Gai’s shoulders, the way he looked with his flushed face and lips parted, sends a rush of blood straight to Gai’s groin. Gai wants him, but he needs time and space to sort through his muddled feelings and figure out whether he wants Kakashi because he’s an Omega, or because he’s Kakashi and just so happens to be an Omega which makes a relationship slightly more possible than it would have been had Kakashi presented as an Alpha, like Gai, and probably the rest of Konoha, had assumed that he would.

_Oh._

“I’m so sorry for what I said before.” Gai’s babbles. This isn’t the best time for apologies but he can’t _not_ now that he’s realised how insensitive his earlier declarations had been about how they would compete to see who would be the better Alpha. “About you being an Alpha. I just assumed that because you’re –” There is no good way to end that sentence. “This doesn’t change – ” No, actually it changes quite a lot. Kakashi’s body is quite literally changing. His status in society will shift. And now Gai is thinking about having sex with his best friend. “You’re my eternal rival and this doesn’t change who you are as a person,” he finishes decisively.

Kakashi whimpers weakly in response, which means that Gai will need to repeat the sentiment at a later date, to make sure that Kakashi understands he has Gai's wholehearted, unquestioning support and respect, regardless of his endotype. 

As a positive, that means that Gai will be able to compose a much more articulate and poignant speech.

Gai sits up straight, bracing his full weight against the door, assuming a guard position. Self-control is not something that he has ever lacked in the past. He can get through this. He studiously ignores his own raging erection, and breathes through his mouth to avoid being overwhelmed by the sweet scent that clings to his clothes and seeps under the doorframe.


	3. Chapter 3

**Summary for the Chapter:**

> Kakashi suffers through his first heat. Gai bashes his head against a door, again and again.

Kakashi’s shirt is soaked through with sweat. He thrashes on the bed trying to remove it. If he could he would just rip it off, tearing the fabric into shreds to get it away from his hot, over sensitive skin, but all the strength has left his body and he feels as weak as a new-born kitten. All he can do is pull at the clothing ineffectually, sitting up despite the protestation of his abdominal muscles, struggling to get it up and over his head. 

When it gets stuck around his ears, pinning his arms up above his head and blinding him, it is all he can do not to cry in frustration and discomfort. 

A rising tide of dizziness threatens to overwhelm him and he whimpers, quiet and soft, as he fights to stay sat upright. Hearing such a vulnerable noise emerge from his own throat both confuses and angers Kakashi in equal measure. He loses his concentration and collapses back on to the bed, his upraised arms scraping awkwardly against the headboard on the way down. 

Disorientated and uncomfortable, Kakashi tries to find some measure of relief by squeezing his eyes shut tight, scrunching his nose and wrinkling his forehead. The effort is futile. The room continues to spin and his body feels as if it’s getting hotter and hotter with every second passing. 

A bead of sweat trickles down his forehead and into the corner of his normal eye. After a long moment, he blinks it open, welcoming the sting of the salt and the momentary clarity that the pain brings. 

A surge of bitterness fill his chest. He snarls, compensating for his weakness with aggression, but the sound is muffled by the double layer of fabric that covers his mouth and the resulting noise is more wretched than threatening.

It was never meant to be like this.

He’s killed more men than he can count. The size of the bounty on his head makes him one of the most attractive targets in all the five nations. He can evade and dismantle traps set by ANBU. He’s strong. He’s fast. He’s deadly.

And yet, here he is, defeated by his own shirt.

Distress bleeds in to anger. He growls and surges upright. Sheer force of will grants strength to his limp limbs. Yanking upwards, he frees himself in one violent movement, and throws the damp fabric across the room in disgust. The dull thud it makes as it hits the wall is more satisfying than it ought to be.

Kakashi lets himself fall back on to the bed with a touch more dignity that before, but the exertion makes him pant heavily all the same. 

The victory is short-lived. 

It’s not enough. He stares up at the ceiling, but his vision blurs and tilts. He can’t get enough air into his lungs. His cloth face mask is damp and heavy from a mixture of sweat and saliva, clinging to his lips. He needs to _breathe._

Using both hands, he slips shaking fingers underneath the bottom hem of the mask and starts to gently roll the material up and over his head. The disaster with the shirt taught him that he needs to take things slowly, be careful and focused, if he wants to get anything done at all while he’s in this condition. 

As soon as Kakashi’s face is fully bare, he sighs in relief, lips parted. He doesn’t throw the mask across the room like he did the shirt. He doesn’t have the energy. Instead he holds it limply in his left hand and lets it drop on to the sheets beside him. 

Liberating his upper half has helped, but not as much as he hoped it would. Spreading his arms wide, creating more space between them and his torso, alleviates a little more of the discomfort. But he’s still unbearably hot, with rivulets of sweat making their lazy way down his chest.

The ability to take his own clothes off is not something he ever thought he would be celebrating quite so sincerely.

In all honestly, it had never occurred to Kakashi that he would present as an omega. It had just seemed… unlikely. 

Then again, he had never given his potential endotype too much thought. It was something that he had no control over, could do nothing to change, and had no hope in hell of preventing, so there seemed little point in agonising about it. It would happen when it happened. The end.

If he had fussed and fretted, like so many of his contemporaries had, especially as a young teen, then maybe he would have been better prepared for handling this. 

No, actually on second thought, no amount of research would have helped him to prepare for the heat and the spikes of lust and the overwhelming urge to put something _inside_ him. 

Fuck, he can’t even gather enough mental energy, or string enough coherent ideas together, to have a coherent existential crisis.

The thought makes him giggle, a sound that borders just on the wrong side of hysterical.

“Kakashi?” Gai calls through the door, voice strained. “Are you alright?”

No, no he’s not alright. His body is on fire. His boxers are soaked through with the slick that his body is producing, intended to lubricate his entrance for penetration by a mate, and he doesn’t want a mate, has never wanted a mate, except now part of him, a very vocal part of him, does want a mate. 

It is one of his life’s greatest tragedies that he doesn’t know enough curse words to appropriately express exactly how not alright he is with the current situation.

What Kakashi actually says in reply, as conversationally as he can manage, is, “Fine, thank you. Just dandy. Wonderful.” The final word is bitten off by a sharp moan as a shiver wracks through his entire body, making him convulse and arch his spine. His entrance clenches and unclenches and suddenly he’s overwhelmed by feelings of aching need and pitiable emptiness. A moment later, after a futile attempt to modulate his breathing, he bids farewell to the last vestiges of his pride and speaks again. “You wouldn’t happen to have anything I could put inside me, would you?”

Gai makes a noise somewhere between a bitten off yelp and a whimper. A second later it is followed by a dull thud and then muffled cursing.

The heavy scent of the other man’s lust creeps under the gap in the door and permeates the bedroom. Kakashi stares at the ceiling, pupils dilated and eyes unseeing.

Oh.

_Oh._

“It hurts, Gai. Please,” Kakashi begs shamelessly. “Please, I need you to help me.” It would appear that he has bid farewell to the part of his brain that moderates impulse control. “I want you.”

There’s another strangled sound from Gai, followed by three dull thuds as the man beats his own head against the door.

Kakashi scrambles out of the bed, toppling to his knees on the floor, and makes his way on all fours towards the door. A single-minded determination to get to Gai is the only thing keeping his wobbly limbs from collapsing beneath him. With every step he takes, the scent of the other man’s lust intensifies, which in turn drives Kakashi wilder. It’s a vicious cycle of heat and lust and bodily fluids leading to more lust and more heat.

By the time he reaches the door, he’s quivering in a heady mixture of desire and exhaustion, pain intermingled with flashes of pleasure. Gai hasn’t replied, but from this closer proximity Kakashi can hear the other man’s laboured breathing, fast and shallow. The sound sets his imagination alight. In his mind’s eye, he sees Gai with his face flushed pink in desire and his lips parted open, bruised red from passionate kisses. 

He wants to crawl into the other man’s lap, wrapping his legs around Gai’s waist and pulling him close. Chest to chest they could rub up against each other, scenting each other’s necks. He could sink down on to Gai’s cock, filling himself up completely. 

Kakashi whimpers and reaches for the brass door handle, rising on to his knees. The handle moves, but the door itself doesn’t budge. Kakashi blinks in confusion. He pushes against the door, throwing his whole weight against it, but the action is futile. He wiggles the handle again, and in a moment of brief clarity, realises that Gai must be holding it closed with his body. “Gai, open the door,” he pleads. “I know you want me.”

"You don't know what you're saying. It's the heat." Gai reasons, a desperate edge to his voice.

He might be right, but it doesn’t matter. Nothing matters except finding relief. He palms at his own erection through his trousers, but there’s not enough of the right kind of friction with his trousers in the way and he already knows anyway, as a matter of biological intuition, that any pleasure he gives himself will fall woefully short of what he needs right now.

He needs Gai in here. Gai would be able to take care of him.

Gai has always been there for him when he needed him most.

Kakashi racks his brain for things he could say that would appeal specifically to Gai. "I challenge you to outlast me in bed." Gai chokes in response, but doesn't make any move to burst through the door and ravage him. Disappointing. It was worth a try. 

He glares at the door as if it were personally responsible for his current woes. Why did Gai have to have a door to his bedroom anyway? Ridiculous.

Fuck, now he’s the one being ridiculous. He’s not even making sense to himself in his own mind. This must be what it means when people talk about omegas being heat-crazed. 

He rests his forehead against the door, savouring the feeling of cold wood against his flushed skin. 

"It hurts, Gai. Please." He's begging but he just doesn't care, not when his whole body feels like it's on fire. He turns around so that he can lean heavily against the door, his legs stretched out in front of him.

There's silence from the other side if the door and then Gai says, uncharacteristically quietly, as if he's unsure of what he's offering. "I could try to talk you through it."

"Yes." Kakashi latches on to the idea. “Yes,” he says more firmly. If he can get Gai talking, get him involved, then maybe he can convince him to open the damn door and come inside. He can’t imagine Gai engaging in dirty talk, in this or any universe, but he isn’t about to look a gift horse in the mouth.

Gai clears his throat and Kakashi tenses in anticipation, excited to see how Gai proceeds. “Take your clothes off.”

Kakashi scrambles to obey, pushing himself to his feet gracelessly. Long fingers quiver as they unclasp his trousers and push the material down past his hips. He stumbles as he steps out of them, but steadies himself by bracing a hand against the door. 

He feels his heat beat start to accelerate in anticipation of what will come next. He lets out a long shakey breath, full of expectation and lust and relief at the promise of an end to this wreckage that is his current reality, but also tinged with anxiety. 

He frowns to himself, identifying his own hesitancy only as it breaches the surface. Kakashi hadn’t thought this far; intent only on his own pain and discomfort and the belligerent demands of his body there hadn’t been any room to consider the consequences of his actions. There wasn’t any room to think.

Was this even really him? 

Drawing in a gulping breath of air, Kakashi then releases it in stuttering gasps, trying desperately to cling to those strands of thought and weave them together. 

A wave of heat crashes through his body and he drops heavily to his knees, barely feeling the pain of the impact in the face of the lust and heat and dizziness surging through him. All attempts at thinking are abandoned. His body aches, and it aches with the most vivid intensity. Now that he’s naked, the slick glistens in the trails where it has escaped down his upper thighs.

Not having a mate here with him hurts. It is a hurt that is both psychological and physical. His entrance clenches and unclenches again and again, trying to grip on to something that isn’t there. 

He moans, low and ragged, a sound torn between pain and pleasure.

“Kakashi?” Gai’s voice is rough, and the deep, masculine, _alpha_ sound of it makes Kakashi moan again; this time in unbridled desire. Silence reigns for all of a moment, before Gai erupts into a torrent of vicious and inventive swearing, followed by more dull thuds. 

Kakashi blinks slowly, his bleary mind struggling to reconcile the idea of Gai, sunshine and happiness and you-shouldn’t-be-reading-porn-in-public-it-might-corrupt-the-youth Gai, with the filthy invocations floating through the air. 

“Gai?” He questions, the confusion momentarily pulling him back to reality.

It is deeply unfortunate that reality means being completely naked in Gai’s bedroom and suffering gracelessly through his first heat; drenched in sweat, and begging Gai to fuck him.

His breath catches in his throat; a chaotic war between primitive instincts and cerebral rationale is waged in the blink of an eye.

Kakashi thinks, with wry amusement, that he is standing in the eye of the storm. This is a brief moment of stillness, suspended in time between the turmoil created by the raging demands of his biology.

This isn’t what he wants.

It might be what his body wants, what his blood and bones are singing out for, but it isn’t what he wants.

“I don’t -” he starts to say, but loses track of where his own sentence was going. It was something important. Something he really needed to say. His jaw clenches in concentration. His hands are trembling.

“This isn’t right,” Gai says, his voice breaks through the silence, thick with grim determination. Kakashi feels as if a weight has been lifted off of his chest. “I won’t talk to you. I won’t say anything. I’m going to stay right here and guard the door. I would lay down my life before letting anyone near you. You should - ” He gulps audibly. “You should go to the bed and touch yourself. This is your first heat so it should break soon. I swear to you that you are safe here, Kakashi.” 

Kakashi nods in acknowledgment, oblivious to the fact that Gai can’t see the movement, and starts to shuffle towards the bed in unthinking obedience.

The journey is long and arduous, although it passes in less than a minute.

Kakashi climbs into the bed face-forward, and then turns so that he is sprawled on to his back with his legs bent at the knee. He grasps his own cock with one hand, pumping eagerly but without rhythm, whilst he uses the fingers of his other hand to thrust in and out of his entrance. It’s not something he’s ever done before, but he lets instinct and primal need guide him forwards.

He moans and writhes, quickly forgetting his own misgivings. Gai’s scent, thick with lust but tinged with the acrid smell of self-loathing, drifts under the door, and it acts as a goad to Kakashi’s pleasure. He begs and pleads for Gai to fuck him, but Gai doesn’t speak again. 

His attempts to pleasure himself are malcoordinated at best, but eventually the heat breaks. 

He stares unseeing at the ceiling and takes stock of his situation. “I need to use your shower,” he says, voice rough from over-use. Covered in a cocktail of his own bodily fluids, Kakashi is too exhausted and sticky to even attempt anything beyond than bathing right now.

There’s a pause before Gai replies.

“I’ll leave a towel in the bathroom. And clean clothes.” Gai tries to channel his usual cheer and self-assurance, but the attempt falls somewhat flat. “I’ll wait in the kitchen for you. Take your time.”

Kakashi tracks the sounds of Gai’s progress through his own apartment. When he hears his footsteps enter the kitchen, and the door close behind him, Kakashi judges it a good enough time as any to pull himself together and get himself cleaned up.

He feels strung out: both stiff and floppy at the same time. It is with great mental fortitude that he drags himself out the bed and towards the promise of hot water.

…

Kakashi is shaky on his feet as he enters the kitchen. He can’t even bring himself to be annoyed when Gai pulls out a chair for him to sit on. It’s not as if Gai wouldn’t have done the same thing before this all happened, he tells himself. It’s just Gai being Gai.

Gai has an erection but it making a valiant effort to ignore it. As valiant an effort as can be made in spandex, anyway.

Kakashi side-eyes him, but in his shattered state can’t think of any jokes or witticisms that wouldn’t open up the possibility of having to discuss the shadows of lust looming over their friendship. And that is not something he wants to do. Not now, and if the world is kind to him, not ever.

“This is your apartment.” Kakashi comments instead, purposefully phrasing it as an observation rather than a question, and then curses himself silently because that’s another conversation that could border dangerously on acknowledging the magnetism he knows, knows but desperately wants to deny, they both felt during his heat. 

It was just hormones, he tells himself.

Gai has the decency to blush. “I’m not sure -” he starts to say and then cuts himself off. He takes a deep breath and tries again, looking Kakashi dead in the eye, willing the other man to believe him. “I panicked.”

Kakashi hums non-committedly in response. It makes sense. Primal instincts taking over. Protect and shelter an omega from threats and any other alphas.

Gai clears his throat. “I’ll go get a medic. They do home visits for things like this.” He stands awkwardly and leaves the room, breaking into a run as soon as he’s out the door.

Being left alone in Gai’s apartment, the scene of the crime as it were, after embarrassing himself so thoroughly isn’t high on Kakashi’s list of ideal ways to spend the afternoon, but he makes the most of it by whipping out his copy of Icha Icha and trying his damnedest to pretend that he didn’t lose all sense of his decency and spend what seemed like hours jerking himself off in Gai’s bedroom, with Gai on the other side of the door, all the while begging the other man to fuck him.

Kakashi bites back a groan, and presses his face into the book. The world’s worst hiding place, Kakashi thinks to himself, and giggles in despair.

It was just biology, he repeats to himself like a prayer. It was just hormones.

But that train of thought inevitably leads him back to the stark reality that he has presented as an omega, which is another thing that he has little interest in confronting any time soon. Saying that it was unexpected would be an understatement. He doesn’t want to talk about it with Gai, and he definitely doesn’t want to talk about it with a medic he doesn’t know. He wants to go home, maybe stop by the memorial on the way there to vent a bit to Obito, and go to sleep.

Fortunately, or maybe unfortunately, it doesn’t take long for Gai to return, medic in tow. 

Gai settles against the sink, behind where Kakashi is sitting, which leaves the vacant chair opposite for the medic.

After sitting down the medic pulls a pen and paper out of her bag to make notes. Then she gets straight to business. “Gai tells me that you’ve just had your first heat.” She’s upbeat and cheery. Kakashi resents her on principal. “How long did it last?” 

Kakashi doesn’t know so he opts for staring at the medic blandly until her smile falters and she turns her attention to Gai instead.

“Two hours and fourteen minutes,” Gai supplies without hesitation, as if he’s giving a mission report.

“Right,” she soldiers on. “That’s not out of the ordinary. The first one is usually a short one. It’s your body’s way of saying, ‘Hello! Look at me! Time to find a mate!’” She chuckles to herself, oblivious to the discomfort of her captive audience. “I’m going to give you some medication to help you deal with the after-effects of your micro-heat, and some pills that will suppress your scent and prevent your hormones from fluctuating too wildly over the coming months. You can choose not to take them, but as an active Shinobi I wouldn’t advise it. Without them you might find yourself having sudden mood swings and craving physical touch. You’ll crave physical touch anyway, mind you,” she clarifies with a cheery smile. “But the medication will make it a mild inconvenience, like an itch you want to scratch, whereas without the medication there’s a real possibility of crying fits and panic attacks if you go too long without skin-on-skin contact.”

Gai’s face is an open book on the best of days, so the distress that is clearly plastered over his features doesn’t surprise Kakashi in the slightest. What is mildly alarmed, on the other hand, is that all of his own years spent suppressing and masking his emotions can’t keep the slack-jawed horror off of his own face. 

“Don’t worry!” The medic hurriedly reassures them. “It doesn’t have to be sexual contact. Something as simple as a hug usually does the trick.” She beams at them, as if that’s supposed to make everything fine and dandy. “Now, you’ll have your first full heat in three months’ time. With your body just coming into its endotype, it can be dangerous and damaging to suppress it, so it’s policy not to prescribe omegas with any medication to prevent them from undergoing their first full heat. It’ll last three days. The medication I’m giving you now serves the dual purpose of acting as a contraceptive. In the future, once your body has finished developing, you’ll have the option to skip heats.” Having finished her spiel, the medic’s gaze turns assessing as she looks between Kakashi and Gai. “But within an established relationship, I doubt you’ll be wanting to do that anyway. Especially after you’ve enjoyed the first full heat together in three months’ time.” She winks conspiratorially at Kakashi.

Kakashi stares at her in response, he’s vaguely aware that Gai is choking on his own tongue in the background, but he doesn’t have the will-power or the strength to object. He just wants her to give him the damn pills and leave so that he can put all of this behind him. “Thank you,” he says, silently congratulating himself on how neutral his voice sounds, and stretches out a hand in a non-verbal request for the medication. 

The medic obliges. “Not a problem! If you have any issues, just come down to the hospital and -” but she’s already been ushered out the apartment and Kakashi is barely clinging to his last shred of patience so he doesn’t feel guilty at all about shutting the door in her face.

When Kakashi turns around, Gai is blushing all the way to the tips of his ears and gawping in his direction like a deer caught in the headlights. 

At least he’s stopped choking, Kakashi thinks to himself.

Gai opens his mouth to speak, but then must think better of it because a moment later he closes it. He clears his throat and tries again. “I’ll take you home,” he declares, flashing a weak grin in Kakashi’s direction.

Kakashi narrows his eyes. “I’ll take myself home,” he snaps, any remaining façade of calm shattering in an instant as he turns on his heel and, with as much dignity as he can muster, flees the apartment.

**Notes for the Chapter:**

> Do you ever write 3k words of smut at 2am in the morning like FILTHY FILTHY WORDS ARE FLOWING FROM MY FINGERTIPS LIKE MAGIC and then spend months slowly and arduously writing the plot that goes with that porn? I do. I do. And then as you write plot the plot starts multiplying, like it's reproducing with itself. And then suddenly you have flashing lights screaming that you should really be addressing the socio-economic impact of having an a/b/o society, and how you need to treat these sorts of issues carefully, but a/b/o isn't even a real thing and all you wanted to do was write the smut you were craving but couldn't find that first night at 2am in the morning.
> 
> This chapter is not that smut, in case you were wondering.
> 
> .........
> 
> Thank you for all the lovely and supportive comments, I really really appreciate them and each and every one makes me smile! I'm sorry for not replying yet, I'm about to get to that now!


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